Human peripheral blood lymphocytes stimulated in vitro with phytohemagglutinin synthesize extra copies of unique sequence element DNA having a complexity of about 10 percent of the genome, previously identified as "excreted DNA" sequences. During log growth this DNA moves from high molecular weight form into the Hirt supernatant fraction, from which it can be released into the culture medium by treating the cells with 1 microgram/ml trypsin for five minutes at 37 degrees C. This trypsin-released DNA will be studied to determine its intracellular location prior to release, to assess its potential association with the cytoplasmic membrane, and to determine whether it is released in a particle associated with protein or lipid. Other membrane active compounds such as lectins and potential inhibitory compounds such as c-AMP will be studied to determine their effect on the release mechanism. Purified DNA will be studied by reassociation kinetics analysis to determine if the unique sequence elements in excreted DNA are associated with repetitive sequence elements. In addition, RNA-DNA reassociation experiments will determine whether excreted DNA is transcribed.